well, this week president obama put syrian leader bashar al assad on notice specifically about the use of chemical weapons, and now we know why. pentagon sources tell nbc news syria is preparing chemical weapons for their possible use against the syrian people in the form of aerial bombs. >> reporter: as the fighting grows more intense and syrian rebels close in on damascus, the syrian regime has turned increasingly desperate. u.s. officials tell nbc news the syrian military has now loaded the precursor chemicals for seron nerve gas into aerial bombs that could be dropped from dozens of syrian fighter bombers. this week u.s. intelligence detected a flurry of activity at chemical weapons site, like this one near homs. while u.s. officials confirmed the precursor chemicals are loaded and they must be mixed together to get the sarin gas. president obama and hillary clinton issued strong warning to syria's president bashar al assad. >> it's the point of no return. they're going to lose any sort of backing they had in terms of the chinese and russians. it's a suicide mission. >> reporter: t